lord loh. said:Can I safely say that PLCs work parallel while the microController works in a sequential manner?
And can Rungs be interchanged in a ladder diagram?
Thanks in advance.
lord loh. said:Can I safely say that PLCs work parallel while the microController works in a sequential manner?
lord loh. said:And can Rungs be interchanged in a ladder diagram?
Thanks in advance.
BeeBop said:I have a couple of PLCs, made by Comfile Technology. They are no where near as expensive as Allen Bradley, or Siemens, but seem to function as well. They are programmed in ladder logic, and appear to run parallel processes. I didn't find programming them all that interesting; no where near as challenging as a microController. The one sitting in front of me has both an Atmega16 and a PIC 16c712. The other, more powerful one, is sealed in a case so I don't know what is in there.
Leftyretro said:I can say that in the industrial control world PLCs are considered 'fast' devices.
Nigel Goodwin said:Like I said, as fast as they need to be, the 'real world' is a relatively slow place - but in processor terms not very fast at all. It's always a bit of a shock using PIC's etc. for robots and mechanical control of any kind, because you find you spend almost all the processors time just wasting time.
Like I said, as fast as they need to be, the 'real world' is a relatively slow place - but in processor terms not very fast at all. It's always a bit of a shock using PIC's etc. for robots and mechanical control of any kind, because you find you spend almost all the processors time just wasting time.
I think you'll find that time is money and the amount of money spent on paying an engineer to design, manufacture and test a custom built module will far outweigh the cost of buying a PLC and paying a technician to program it.arunb said:Quite true indeed, but I suppose the low cost of a micro-controller should justify this wastage of time,
Have you ever programed a PLC before?I find that in most industries engineers are reluctant to modify or edit an existing program as there is a danger of the new program having bugs in them, and so causing loss in production....
No, not most of the time.in such cases it may be easier to design a proprietary system that uses a PIC or any other mcu...
Hero999 said:I think you'll find that time is money and the amount of money spent on paying an engineer to design, manufacture and test a custom built module will far outweigh the cost of buying a PLC and paying a technician to program it.
Have you ever programed a PLC before?
I don't have a lot of experiance but I leant to do it at collegfe in a couple of lessons. PLCs are very easy to program, ladder logic is purely graphical, the program looks like a circuit made with relays, switches and timers; understanding and modifying a PLC program is as easy as reading a schematic.
No, not most of the time.
I would recommend PLCs in most control applications from traffic lights to conrtoling a plant watering and heating system in your greenhouse. A PLC gives you the confidence that the hardware is properly designed and providing you don't abuse it the most likely error is your programming.
The only time I would say that microcontrollers are more cost effective in control systems is when they're integrated into mass produced items like cars.
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